have been looking around, but I have not found an answer that helped me out. I am wondering how I can keep the scroll position in a scrollview when I move forwards and backwards in a navigation controller. Currently, when I go to another view in the navigation controller, the scroll view resets and is at the top when I go back. Any code would be greatly appreciated. Sorry if my explanation was not good enough. So far this is what I have, I know that this won't work, but what should I do?
- (void)viewWillAppear:(BOOL)animated {
scrollView.contentOffset.y = scrollSave;
[super viewWillAppear:YES];
}
- (void)viewWillDisappear:(BOOL)animated {
CGFloat scrollSave = scrollView.contentOffset.y;
[super viewWillDisappear:animated];
}
The code you have above shouldn't even compile. You could save this scroll position in another variable, but generally the scroll position shouldn't be resetting itself anyway. You should remove any code that is trying to manipulate the content offset at all, and see if it restores it to the correct scroll position upon returning to the view.
With your current approach, scrollSave is a local variable declared in viewWillDisappear so you cannot access the value in viewWillAppear. You will need to create an instance variable or a property. (If the view controller is still in memory, it should maintain the contentOffset so this might not be necessary)
#interface MyViewController ()
#property (nonatomic) CGPoint scrollSave;
#end
#implementation MyViewController
- (void)viewWillAppear:(BOOL)animated {
[scrollView setContentOffset:self.scrollSave];
[super viewWillAppear:YES];
}
- (void)viewWillDisappear:(BOOL)animated {
self.scrollSave = scrollView.contentOffset;
[super viewWillDisappear:animated];
}
Now there is an issue with persistence. If the you navigate back in the navigation controller, this view controller will be released from memory. If you need to save the users position then I would suggest using NSUserDefaults.
#interface MyViewController ()
#property (nonatomic) NSUserDefaults *defaults
#end
#implementation MyViewController
- (void)viewWillAppear:(BOOL)animated {
CGPoint scrollSave = CGPointFromString([_defaults objectForKey:#"scrollSaveKey"]);
scrollView.contentOffset = scrollSave;
[super viewWillAppear:YES];
}
- (void)viewWillDisappear:(BOOL)animated {
[_defaults setObject:NSStringFromCGPoint(scrollView.contentOffset) forKey:#"scrollSaveKey"];
[_defaults synchronize];
[super viewWillDisappear:animated];
}
Kyle's answer should get you storing the variable okay, but in regards to assigning the contentOffset.y, trying animating the scrollview.
[scrollView scrollRectToVisible:
CGRectMake(scrollView.frame.origin.x, scrollSave.y, scrollView.frame.size.width, scrollView.frame.size.height)
animated:NO];
That code would go into viewWillAppear.
Related
I have implemented a basic slider using iCarousel iOS library but i dont know how to make it as a Auto slider instead of manual swipe sliding.
Here is my sample project code Pls help me
Code
When i searched in google i got this link,but i didnt understand anything
https://github.com/nicklockwood/iCarousel/issues/84
This solved my problem
in ViewDidAppear() i have added following line
-(void)viewDidAppear:(BOOL)animated
{
sliderCount=0;
[super viewDidAppear:animated];
[NSTimer scheduledTimerWithTimeInterval:3.0f target:self selector:#selector(runMethod) userInfo:nil repeats:YES];
}
-(void)runMethod
{
[self.carousel scrollToItemAtIndex:sliderCount animated:YES];
if(sliderCount== 7)
{
sliderCount=0;
}
else
{
sliderCount++;
}
}
In your ViewDidLoad method in your Viewcontroller.
- (void)viewDidLoad
{
[super viewDidLoad];
//configure carousel
carousel.type=iCarouselTypeCylinder;
carousel.autoscroll=0.4;
}
Looking at the github link, I assume you want to autoscroll to an item upon view.
You have defined the function
- (void)scrollToItemAtIndex:(NSInteger)index animated:(BOOL)animated
However this isn't part of the iCarousel delegate, its already defined as part of the class, therefore you just need to call it. Putting it in viewDidAppear would seem appropriate if you wanted it to auto scroll to a particular index when your view controller was presented to the user. Simply add the method below.
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
// The index of 3 was just chosen as an example
NSInteger chosenIndex = 3;
[self.carousel scrollToItemAtIndex:chosenIndex animated:YES];
}
- (void)viewDidLoad
{
[super viewDidLoad];
carousel.type=iCarouselTypeCylinder;
carousel.autoscroll=0.8;
[carousel reloadData];
}
I have a screen, which contains multiple UIImages (their amount and size are known only at runtime, so i add them programmatically) and some fixed buttons below these UIImages.
How to make buttons display certainly under all Images?
I've tried
1.) Put Buttons and Images into 2 separate views, and then add constraint between them. No result, buttons are hidden behind images.
2.) Put buttons into separate view and set constraint in code, (tried both viewDidLoad and viewDidAppear). Constraint is set between container view and top of the screen, depending on size and amount of images.
Example of code:
-(void) viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
NSInteger totalImages = [self.object.fullphotos count];
self.labelsTopConstraint.constant = totalImages*(imageHeight + 20) + 10;
}
In case 2 buttons are positioned right, but don't respond to touches.
How should I layout everything correctly?
Thanks in advance!
Take a Tableview for those images and add buttons in a last cell.
The best way is creating a Object with a refresh method that can be called in viewDidAppear
MyObject.h
#interface MyObject : UIViewController
#property (nonatomic,strong) UIImageview *img;
#property (nonatomic,strong) UIButton *btn;
- (void) refresh;
in MyObject.m
- (void)viewDidLoad {
[self.btn addTarget:self action:#selector(myMethod:) forControlEvents:UIControlEventTouchUpInside];
}
- (void) refresh {
//make your settings here
}
-(void)myMethod {
//your button action here
}
Then in your controller if you have your objects in an NSArray:
-(void) viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
for (MyObject *myObj in objectsArray) {
#autoreleasePool {
[myObj refresh];
}
}
}
I have a UICollectionView that is used to simulate the new calendar in iOS 7. This collection view is inside a controller that has a selectedDate property. Whenever the selectedDate property is set the collection view should scroll to the date in the collection view.
The calendar controller's viewWillAppear also ensure the selected date is visible because this controller is cached and reused.
-(void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[self.calendarView scrollToDate:[self selectedDate] animated:NO];
}
The problem is that the VERY first time the calendar controller is shown the scroll does not work. The contentOffset of the collection view is not updated.
My current workaround is to schedule the scroll to occur on the next run loop using
dispatch_after(DISPATCH_TIME_NOW, dispatch_get_main_queue(), ^(void)
{
// Scroll to the date.
});
It looks like when the UICollectionView is not in a window you cannot scroll. Scheduling the scroll to happen on the next run loop ensure that the view has been added to the window and can be properly scrolled.
Has anyone else experienced this issue and what their workarounds?
you can always force auto-layout to layout.
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
self.view.layoutIfNeeded()
self.collectionView.scrollToItemAtIndexPath......
}
If you are using auto layout, the issue may be that the constraints haven't set the frames yet. Try calling the scrollToDate: method in viewDidLayoutSubviews (without dispatch_after).
#interface CustomViewController ()
#property (nonatomic) BOOL isFirstTimeViewDidLayoutSubviews; // variable name could be re-factored
#property (nonatomic, weak) IBOutlet UIScrollView *scrollView;
#end
#implementation CustomViewController
- (void)viewDidLoad
{
[super viewDidLoad];
self.isFirstTimeViewDidLayoutSubviews = YES;
}
- (void)viewDidLayoutSubviews
{
// only after layoutSubviews executes for subviews, do constraints and frames agree (WWDC 2012 video "Best Practices for Mastering Auto Layout")
if (self.isFirstTimeViewDidLayoutSubviews) {
// execute geometry-related code...
// good place to set scroll view's content offset, if its subviews are added dynamically (in code)
self.isFirstTimeViewDidLayoutSubviews = NO;
}
bilobatum's answer is correct!
I'm writing this because I don't have reputation to comment... :/
I tried bilobatum's answer in my project, and it worked perfectly!
My code:
-(void)viewDidLayoutSubviews{
[super viewDidLayoutSubviews];
if (currentOffset.y != 999) {
[collectionView setContentOffset:currentOffset animated:NO];
}
}
currentOsset is a CGPoint initialized with x = 0 and y = 999 values (CGPoint currentOffset = {0,999};)
In the viewWillDisappear method I save the collectionView's contentOffset in the currentOffset.
This way if I navigate to the controller that has the collectionView and I navigated to there before, I will always have the last position.
The code that will work for you:
-(void)viewDidLayoutSubviews{
[super viewDidLayoutSubviews];
[self.calendarView scrollToDate:[self selectedDate] animated:NO];
}
Thank you bilobatum for the answer!
Using -viewDidLayoutSubviews created an infinite loop that made the solution too complicated.
Instead I just added a small delay to let the constraints be created before the scrolling:
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
if ([self.scheduleDate isThisWeek]) [self.calendarLayout performSelector:#selector(scrollToCurrentTime) withObject:nil afterDelay:1];
}
I am trying to reload content from local file of UIWebView in viewDidDisappear of UIViewController. Badaccess is caught. But if I write the same code in viewWillDisappear, it works.
What might be the reason?
Once I've heard that UIWebView can't reload its content when it is not visible (not sure about it).
My code (hope it'll be enough):
#interface WebViewController : UIViewController <UIWebViewDelegate> {
ExtendedWebView * webView;
}
#property (nonatomic, retain) ExtendedWebView * webView;
#end
//WebViewController implementation
- (void)loadView
{
[super loadView];
WebViewCachingSingleton * webViewSingleton = [WebViewCachingSingleton sharedService];
ExtendedWebView * newWebView = [webViewSingleton getAvailableWebViewResource];//here I get ExtendedWebView. it works =)
newWebView.frame = CGRectMake(0, 0, 320, 400);
newWebView.delegate = self;
[self.view addSubview:newWebView];
self.webView = newWebView;
}
- (void)viewDidDisappear:(BOOL)animated
{
[[WebViewCachingSingleton sharedService] makeWebViewUnused:self.webView];
}
//WebViewCachingSingleton:
- (void) makeWebViewUnused : (ExtendedWebView *) aWebView
{
aWebView.isFree = YES;
[aWebView reload];
}
It will not work because viewDidDisappear is called when the view is disappeared, so all the subviews are released. The viewWillDisappear is called just before releasing all the objects associated with that view.
So you are trying to call the reload method of a UIWebView that has been already released. That is basically the reason why it crashes.
Hope it helps
The reload can be performed even if not displayed.
I tried to make an example of code to put in your state and have not had any problems.
Try to debug and enable NSZombieEnabled to see what actually happens to your application.
Try to post on any piece of code that might help us give you more details.
So I have a subclass of UITableViewController that loads some data from the internet and uses MBProgressHUD during the loading process. I use the standard MBProgressHUD initialization.
HUD = [[MBProgressHUD alloc] initWithView:self.view];
[self.view addSubview:HUD];
HUD.delegate = self;
HUD.labelText = #"Loading";
[HUD show:YES];
This is the result:
.
Is there any way to resolve this issue, or should I just abandon MBProgressHUD?
Thanks!
My solution was pretty simple. Instead of using self's view, I used self's navigationController's view.
HUD = [[MBProgressHUD alloc] initWithView:self.navigationController.view];
[self.navigationController.view addSubview:HUD];
This should work for the OP because his picture shows he's using a UINavigationController. If you don't have a UINavigationController, you might add another view on top of your UITableView, and add the HUD to that. You'll have to write a little extra code to hide/show this extra view.
An unfortunate thing with this simple solution (not counting my idea adding another view mentioned above) means the user can't use the navigation controls while the HUD is showing. For my app, it's not a problem. But if you have a long running operation and the user might want to press Cancel, this will not be a good solution.
It's probably because self.view is a UITableView, which may dynamically add/remove subviews including the headers, which could end up on top of the HUD after you add it as a subview. You should either add the HUD directly to the window, or (for a little more work but perhaps a better result) you could implement a UIViewController subclass which has a plain view containing both the table view and the HUD view. That way you could put the HUD completely on top of the table view.
My solution was:
self.appDelegate = (kmAppDelegate *)[[UIApplication sharedApplication] delegate];
.
.
_progressHUD = [[MBProgressHUD alloc] initWithView:self.appDelegate.window];
.
[self.appDelegate.window addSubview:_progressHUD];
Works like a charm for all scenarios involving the UITableViewController. I hope this helps someone else. Happy Programming :)
Create a category on UITableView that will take your MBProgressHUD and bring it to the front, by doing so it will always appear "on top" and let the user use other controls in your app like a back button if the action is taking to long (for example)
#import "UITableView+MBProgressView.h"
#implementation UITableView (MBProgressView)
- (void)didAddSubview:(UIView *)subview{
for (UIView *view in self.subviews){
if([view isKindOfClass:[MBProgressHUD class]]){
[self bringSubviewToFront:view];
break;
}
}
}
#end
A simple fix would be to give the z-index of the HUD view a large value, ensuring it is placed in front of all the other subviews.
Check out this answer for information on how to edit a UIView's z-index: https://stackoverflow.com/a/4631895/1766720.
I've stepped into a similar problem a few minutes ago and was able to solve it after being pointed to the right direction in a different (and IMHO more elegant) way:
Add the following line at the beginning of your UITableViewController subclass implementation:
#synthesize tableView;
Add the following code to the beginning of your init method of your UITableViewController subclass, like initWithNibName:bundle: (the beginning of viewDidLoad might work as well, although I recommend an init method):
if (!tableView &&
[self.view isKindOfClass:[UITableView class]]) {
tableView = (UITableView *)self.view;
}
self.view = [[UIView alloc] initWithFrame:[UIScreen mainScreen].applicationFrame];
self.tableView.frame = self.view.bounds;
self.tableView.contentInset = UIEdgeInsetsMake(0.0, 0.0, 0.0, 0.0);
[self.view addSubview:self.tableView];
Then you don't need to change your code you posted in your question any more. What the above code does is basically seperating the self.tableView from self.view (which was a reference to the same object as self.tableView before, but now is a UIView containing the table view as one might expect).
I've Just solved that issue manually , it has been 2 years since Chris Ballinger asked but maybe someone get used of what is going on here.
In UITableViewController i execute an HTTP method in viewDidLoad , which is running in background so the table view is loaded while the progress is shown causing that miss.
i added a false flag which is changed to yes in viewDidLoad, And in viewDidAppear something like that can solve that problem.
-(void) viewDidAppear:(BOOL)animated{
if (flag) {
[self requestSomeData];
}
flag = YES;
[super viewDidAppear:animated];
}
I had the same problem and decided to solve this by changing my UITableViewController to a plain UIViewController that has a UITableView as a subview (similar to what jtbandes proposed as an alternative approach in his accepted answer). The advantage of this solution is that the UI of the navigation controller isn't blocked, i.e. users can simply leave the ViewController in case they don't want to waiting any longer for your timely operation to finish.
You need to do the following changes:
Header file:
#interface YourViewController : UIViewController <UITableViewDelegate, UITableViewDataSource>
- (id)initWithStyle:(UITableViewStyle)style;
#end
Implementation file:
#interface YourViewController ()
#property (nonatomic, retain) UITableView *tableView;
#property (nonatomic, retain) MBProgressHUD *hud;
#end
#implementation YourViewController
#pragma mark -
#pragma mark Initialization & Memory Management
- (id)initWithStyle:(UITableViewStyle)style;
{
self = [super init];
if (self) {
// create and configure the table view
_tableView = [[UITableView alloc] initWithFrame:CGRectNull style:style];
_tableView.delegate = self;
_tableView.dataSource = self;
}
return self;
}
- (void)dealloc
{
self.tableView = nil;
self.hud = nil;
[super dealloc];
}
#pragma mark -
#pragma mark View lifecycle
- (void)loadView {
CGRect frame = [self boundsFittingAvailableScreenSpace];
self.view = [[[UIView alloc] initWithFrame:frame] autorelease];
// add UI elements
self.tableView.frame = self.view.bounds;
[self.view addSubview:self.tableView];
}
- (void)viewWillDisappear:(BOOL)animated
{
// optionally
[self cancelWhateverYouWereWaitingFor];
[self.hud hide:animated];
}
The method -(CGRect)boundsFittingAvailableScreenSpace is part of my UIViewController+FittingBounds category. You can find its implementation here: https://gist.github.com/Tafkadasoh/5206130.
In .h
#import "AppDelegate.h"
#interface ViewController : UITableViewController
{
MBProgressHUD *progressHUD;
ASAppDelegate *appDelegate;
}
In .m
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
appDelegate = (ASAppDelegate *) [UIApplication sharedApplication].delegate;
progressHUD = [MBProgressHUD showHUDAddedTo:appDelegate.window animated:YES];
progressHUD.labelText = #"Syncing To Sever";
[appDelegate.window addSubview:progressHUD];
This should work.
[MBProgressHUD showHUDAddedTo:self.navigationController.view animated:YES];
And to remove you can try
[MBProgressHUD hideHUDForView:self.navigationController.view animated:YES];